Generally aircraft are divided into two major classifications, one is fixed wing and the second is rotary wing aircraft which are commonly referred to as helicopters. For purposes of substantiating the verity of the invention disclosed herein, comparing categories of prior art aircraft, the following to wit; (1) Wing fan lift aircraft (wing fan)--which are vertical take off and landing (VTOL) fixed wing aircraft that derive their vertical lift from fans, ducted fans, or propellers situated in their respective wings; (2) Tilt rotor/wing aircraft (tilt rotor/wing)--are fixed wing aircraft that have their propellers, rotors, ducted fans or jets situated at or near the tips of their wings or on the wings and said propellers, rotors, fans, wings, ducted fans, or jets are rotated ninety degrees to achieve VTOL flight transitions; (3) Jet assisted duct fans (jet assisted)--which are fixed wing VTOL aircraft employing jet engine or turbo fan engine thrust assisted fans or ducted fans. These aircraft have either their vertical lift augmented by jet or turbo fan thrust or the jet thrust is used to operate a vertical lift fan device in an enjoined manner; (4) Nozzle vectored jet thrust (jet thrust)--which are VTOL fixed wing jet aircraft that derive vertical lift from direct jet thrust channeled and directed by means of directional nozzles to achieve vertical lift and accomplish transitions; (5) Tail setters--a fixed wing VTOL aircraft that takes off vertically from an at rest vertical position standing on its tail and transitions to land the same way; whereby transitions are accomplished by rotating the entire aircraft ninety degrees to achieve VTOL transitions; (6) Various unusual VTOL aircraft.
The aviation industry has sought diligently to contrive an aircraft that can take off, land, and hover like a helicopter; without risk of stalling; and yet can also fly horizontally like a fixed wing airplane without the aerodynamic drag of a helicopter.
To date the closest that this goal has been met is with the Bell Helicopter V-22 Ospray VTOL aircraft. The V-22 is a fixed wing, tilt rotor, aircraft which takes off, lands, and hovers like a helicopter and rotates its' propulsion system 90 degrees to achieve horizontal flight like a fixed wing aircraft.
Other similar VTOL tilt rotor designs of prior art aircraft include the Bell Eagle Eye unmanned aircraft, Boeing Tracer Tilt Rotor unmanned aircraft, Bell XV-3, Curtis-Wright X-100 and X-19.
Tilt rotor prior art aircraft have five distinctive disadvantages. One is that the aircraft cannot land or take off horizontally like a conventional airplane if for some reason there was a failure of its' apparatus that rotates its' propulsion system while in the vertical flight mode. Another is due to their rotor diameters being so large that the rotors would strike the ground in a horizontal landing or take off scenario. Such a large rotor diameter is necessary however, in order for these aircraft to take off and land vertically.
The second disadvantage is that tilt rotor aircraft must overcome negative angular moments created by their spinning rotors when tilting their rotors 90 degrees during VTOL transitions. These forces act against the aircraft's fuselage creating a difficult control and stability phase for the pilot as the aircraft is transitioning in VTOL flight.
A third disadvantage of a tilt rotor aircraft is that they cannot fly at all if one engine should fail. The fourth disadvantage is one that is shared with helicopters in that tilt rotor aircraft, that do not employ jets or ducted fans, take a sizeable area to land in because of rotor diameter. A fifth disadvantage of tilt rotor aircraft, not employing jets or ducted fans, is also shared by helicopters which is exposed rotor blades that can strike nearby objects or people while landing and taking off.
Similar aircraft to the aforementioned are the U.S. ARMYS'/NASA Doak 16, the French NORD 500 and the Bell X-22; all are classed as tilt rotor aircraft in that the aircraft's propulsion systems are similarly rotated 90 degrees to achieve VTOL transitions. However, the X-22, the French NORD 500 and the Doak 16 employ ducted fans instead of rotors. This configuration allows the respective aircraft to land, take off, and hover like a helicopter and yet land and take off horizontally like a conventional fixed wing aircraft; they require less space in which to land and do not have exposed rotors.
The aforementioned tilt rotor ducted fan aircraft have two distinctive disadvantages. One is they likewise have negative angular moments acting against their fuselages to overcome when their respective propulsion systems are rotated 90 degrees during VTOL transitions. The second disadvantage is that they use ducted fans which, when employed in horizontal flight, limits their forward speed. The forward speed limitation of ducted fans is due to the fact that they build up a boundary layer of air immediately in front of the ducts at higher forward air speeds. This limits their forward airspeed to that of helicopters thus limiting their application on VTOL fixed wing aircraft.
Another type of VTOL aircraft known as tilt wing aircraft; as opposed to tilt rotor/ducted fans; are not true fixed wing aircraft. A few of the more well known tilt wing prior art aircraft are: The army/Navy VERTOL Model 76; the LTV/Hiller/Ryan XC142, which was based on the Hiller X18; and the Candair CL-84. These tilt wing aircraft, as the designation implies, tilt their wings 90 degrees with the propellers and engines attached to the wings to achieve VTOL flight transitions. However, they are generally accepted to be VTOL fixed wing aircraft as the wing is in a fixed position during horizontal flight.
Notwithstanding the moveable wing, they do take off and land, as well as hover, like a helicopter and transition to fly horizontally like an airplane. As with tilt rotor and tilting ducted fans, as aforementioned; tilt wing aircraft have to also overcome inherent negative angular moments when their wings are rotated 90 degrees to achieve VTOL flight.
Another problem with tilt wing designs is that the chance of a stall is greater than with tilt rotor or tilting ducts as tilt wing aircraft have a greater difficulty attaining aerodynamic lift on their wings for horizontal flight during part of the transition phase of VTOL flight.
Yet another type of fixed wing VTOL aircraft, known as tail setters, rest on their respective tails, vertically, and take off and land vertically on their tails. To achieve horizontal flight the entire aircraft rotates 90 degrees during VTOL flight transitions. The most notable of this type of prior art aircraft are the Convair XFY1 Pogo, the Lockheed XFV1, and the McDonnel Douglas Sparrow Hawk unmanned aircraft and the Bell X13 Vertiplane.
The most important short coming of tail setter VTOL fixed wing aircraft is the same as that of the tilt wing aircraft with respect to a lack of aerodynamic lift of the fixed wing during VTOL transitions and also having to overcome negative angular moments created by the gyro effect of their spinning propellers when rotated longitudinally from the angle of attack of the aircraft. The one exception being the Bell X13 Vertiplane which employed a jet engine. An additional; yet the most notable; draw back of a manned tail setter was a lack of pilot situational awareness during VTOL transitions.
Other examples of fixed wing VTOL aircraft employ vectored jet engine thrust as a means of providing vertical lift to hover and achieve VTOL flight.
The most notable of this type of prior art aircraft is the British harrier jet aircraft. These type of VTOL aircraft use the thrust of their jet engines vectored by rotating nozzles to accomplish VTOL flight and transitions.
Jet thrust type VTOL fixed wing aircraft have four notable drawbacks in that their jet engine thrust is of such a great magnitude that foreign objects kicked up by the jets tremendous thrust blast create hazardous conditions to both the aircraft and personnel on the ground near the aircraft's landing zone during VTOL landings and take offs. A second draw back is that in order for the aircraft to hover or take off vertically the aircraft's engines must be at or very near full throttle.
For a jet engine aircraft to accomplish hover flight and VTOL flight with full throttle, a tremendous amount of fuel is required thus diminishing the aircraft's horizontal flight time and range. The third disadvantage is the cost of providing such an aircraft due to the complexity of providing hover flight stability and the cost of a specialized jet engine for vertical flight.
Additional examples of employing jet thrust for vertical lift are disclosed in U.S. Pat. No. 3,972,490 issued Aug. 3, 1976 to Vincent H. Zimmermann et al and U.S. Pat. No. 4,171,112 issued Oct. 16, 1979 to Harry M. Harvy of England. The aircraft of U.S. Pat. No. 3,972,490 is a hybrid version combining nozzle vectored jet thrust together with a single ducted fan. This concept is similarly disclosed in U.S. Pat. No. 5,290,428 issued May 11, 1993 to Paul M. Bevilaqua and Paul K. Shumpert. A variation to the aforementioned aircraft is disclosed in U.S. Pat. No. 3,912,201 issued Oct. 14, 1975 to Charles Bradbury of England.
A variation of the above VTOL fixed wing aircraft is depicted as employing a combination of jet thrust and ducted fans as disclosed in U.S. Pat. No. 2,940,691 issued on Jun. 14, 1960 to Constant V. David, and U.S. Pat. No. 3,161,374 issued on Dec. 15, 1964 to Robert W. Allred et al. These last two prior art aircraft have one thing in common in that they both have their vertical lift fans in their wing area. These types of configurations, employing lift fan wings, create a distinctive draw back as will be discussed in the following aircraft prior art disclosures.
A classification of fixed wing VTOL aircraft, generally accepted as being known as lift fan wing aircraft, derive their vertical lift from fixed immovable ducted fans or propellers situated inside the wing area of the aircraft. These aircraft have one distinctive characteristic among them. The area of their wings displaced by the in wing fans severely limit the wings horizontal flight lifting capability due to drag.
The drag of a lift fan wing results from thicker wings required to accommodate the fans and a reduction of wing lift due to the slip stream air over their wings in horizontal flight being disturbed while the fans are in operation.
The only known in the wing lift fan aircraft to work operationally is the Ryan XV-5A and the Lockheed Hummingbird; both are similar to the prior art aircraft disclosed in U.S. Pat. No. 3,080,137. These concepts augment the in wing lift fans' lift by piping jet thrust to them. Another in the wing lift fan aircraft, that was to also augment its' lift by piping jet thrust to their fans, is disclosed in U.S. Pat. No. 3,161,374 but never known to fly.
Other in the wing lift fan concepts of prior art are disclosed in U.S. Pat. Nos. 2,939,649; 3,083,935; 4,125,232; 3,120,362 and 4,828,203; none of these concepts have been known to fly as of the date of this application.
Two prior art concepts disclosed in U.S. Pat. No. 3,559,921 issued Feb. 10, 1967 to Eugene L. Timperman, and U.S. Pat. No. 2,138,999 issued Dec. 6, 1938 to Wilmer W. Clark, show their vertical lifting apparatuses situated in the center body of the aircraft which is similar to the aircraft of U.S. Pat. Nos. 5,209,428; 3,912,201; 2,939,649 and U.S. Pat. No. 2,988,301 issued on Jun. 13, 1961.
In the Timperman patent, a single ducted fan is situated in the center of the aircraft's fuselage for vertical lift and driven by two engines; one in the front of the aircraft and one engine in the aft section of the aircraft. A transmission forward of the ducted fan transfers power to two wing mounted propellers for horizontal thrust.
Like the aircraft disclosed in U.S. Pat. No. 3,912,201; Timperman's aircraft employs thrust from the ducted fan piped to various locations of the aircraft to provide stability while in hover.
The departure of U.S. Pat. No. 3,912,201 from the Timperman disclosure is that the fans thrust is not augmented by jet thrust as is the case in U.S. Pat. Nos. 5,209,428; 3,912,201; and 2,939,649.
Without augmented thrust from some other source, a single ducted fan, proportionally shown in the Timperman disclosure, can not lift such an aircraft vertically according to current technology. However, such a concept could prove to be effective as a short take off and landing aircraft.
The prior art disclosed by Wilmer W. Clark in U.S. Pat. No. 2,138,999 discloses a vacuum lift device that is purported by the inventor to operate on vacuum forces and differences in atmospheric pressure principals that supposedly create a lifting force of several tons with two three foot diameter by three feet deep pressure differential devices.
While the Clark concept is intriguing, the disclosure was made far in advance of actual ducted fan research performed some 20 years later which has subsequently shown that the vacuum lift device is not technologically feasible as disclosed. Indeed, the vacuum lift device, so disclosed, does not have an open bottom; a physical requirement of any ducted fan. The device produces no thrust for vertical lift. It should be evident to the most casual observer upon reading the text of the Clark patent, that generating thrust was not Clark's intent.
The devices disclosed in Clark's aircraft is constructed similar to a modern day washing machine tub and agitator. The agitator is substituted by a multi-blade propeller having a three foot diameter, a three foot cord, and each blade being twisted about their ax's.
The Clark propellers rotate radially in an enclosed tub that is open only at the top. The Clark disclosure is not predicated on any known physical laws or principals as of the date of this application.
Unusual VTOL flying bodies that can not be classified as fixed wing aircraft nor helicopters are represented by the Sikorsky Cypher, the Canadair CL-227 Sentinel, and the General Dynamics Ring Wing Vehicle (RWV) among others; all three disclosed herein are unmanned aerial vehicles (UAVs). The Cypher UAV has a doughnut shaped fuselage with two contra rotating, articulated, rotor blades similar to a configuration used by some helicopters. The blades are situated within the center opening of the doughnut shape fuselage connected by a gear box and drive shaft which is situated at a fixed radius position laterally connected to a power means in the fuselage. The primary advantage of the Cypher is that it does not have exposed rotor blades and can land and take off like a helicopter.
However, the Cypher UAV has several disadvantages. One disadvantage is that the craft hovers all the time. Therefore, it must expend fuel at a higher rate than that of a helicopter or an airplane as little lift is afforded the craft in horizontal flight. As a result of not having wings, the craft suffers a secondary disadvantage of severe controllability problems in horizontal flight. These two draw backs lead to a third disadvantage which is limited range for its' rated flight duration. The combined aforementioned disadvantages also limit the crafts' forward speed. Because the craft hovers all the time it suffers a low maximum altitude rating compared to that of other VTOL flying bodies and aircraft of proportionate size and weight. The Cypher is further disadvantaged by its design in that it has a very low payload carrying capability disproportionate to its' Reynolds class. Having no control surfaces, this aircraft is lacking in aerodynamic directional steering in forward flight.
A prior art aircraft similar to the aforementioned Cypher UAV, is the CL-227; having a somewhat like manner in providing vertical lift in that it has two articulating contra rotating rotors.
The CL-227s fuselage is elongated vertically with the power means in the center of the craft. The overall aircraft resembles the likeness of a flying peanut for which it has been nicknamed. The craft lands and takes off vertically like a tail setter VTOL aircraft/UAV and hovers all the time like the Cypher UAV. One advantage the CL-227 has over the Cypher prior art aircraft is that it is somewhat more controllable in direction during forward flight because its' rotors are exposed to the surrounding slip stream air which provides the craft with some ability, via the articulation of its exposed rotors, to control its direction by the action of slip stream air against its' rotor blades which act as control surfaces during forward flight.
The CL-227s exposed rotor blades excludes its' use in UAV commercial application authorization by the FAA. The CL-227 UAV has virtually the same disadvantages of the Cypher UTAV with the exception of controllability and payload carrying capability.
Like the CL-227 UAV prior art aircraft the General Dynamics Ring Wing Vehicle (RWV) is a VTOL UAV that lands and takes off on its tail like the earlier mentioned prior art tail setter aircraft. The RWV however, employs a ducted fan configuration employing thrust vectoring for directional control. The craft takes off vertically and then rotates its entire fuselage ninety degrees for horizontal flight applications, unlike the Cypher and CL-227 prior aircraft art, with landing being the reverse of this action. In horizontal flight mode, the duct of the ducted fan itself provides lift for the vehicle in horizontal flight and functions as a ring winged aircraft.
While the General Dynamics RWV UAV has no exposed rotor blades, a distinct advantage in commercial UAV applications, it must however, resolve the difficult flight dynamics of negative angular moments like tilt wing and tilt rotor prior art aircraft and the flight dynamic problems of the tail setter prior art aircraft limiting its' use in commercial applications as a UAV because of safety issues involving pilot situational awareness and controlling the craft during VTOL transitions.
A configuration entailing some of the attributes of the Cypher, and some from the RWV aforementioned prior art aircraft, is the manned VZ-9V Avrocar aircraft. Built under a Canadian and U.S. Army/Air Force contract, this prior art aircraft is similar in design to that of a fictional flying saucer. The craft is disk shaped and employs three jet engines for power.
A single ducted fan is situated in the center of the VZ-9V and used as the primary vertical lifting means. The ducted fan is powered by the jet engines. Control and forward motion of the craft is accomplished by thrust vectoring the three jet engines' thrust. The craft suffered from such extreme controllability problems however, that the project was cancelled.
The Piasecki Air Jeep is an example of unusual prior art aircraft that was developed and flown under US Army/Navy contracts between 1957 and 1962. The craft was constructed having a dual power means located at the center of its' fuselage. The power means drove a central gear box, likewise centrally located, which entailed a hydrostatic drive means. The hydrostatic drive means drove two, variably pitched, horizontally mounted, counter rotating, vertical lifting propeller means; one situated in live rear of the fuselage and one in the forward section thereof. Both propellers are shrouded by the crafts' fuselage.
Partial control stability and forward motion of the Air Jeep was accomplished by thrust vectoring. The thrust vectoring means is comprised of a series of thrust vectoring vanes concentrically and evenly situated around the exhaust orifices of the vertical lifting means in a star configuration. Roll, pitch, and yaw control was accomplished by a combination of articulation of the vertical lifting propellers in conjunction with the thrust vectoring vanes. This prior art craft had a number of disadvantages. As the craft hovered all the time, its' range was limited; a result of excessive fuel consumption. The craft derived all of its' forward motion from its' vertical thrust thus limiting its' forward speed. As the craft employed shrouded propellers as opposed to true ducted fans, no inherent gyroscopic roll control was effected due to the lower rotational speeds required of larger diameter shrouded propeller applications versus the higher rotational speeds allowed by the smaller diameter of a ducted fans' rotors.
Likewise, a disadvantage of the crafts' employment of shrouded propellers is that the diameter normally required in such vertical lift applications generally preclude its' application in a fixed wing aircraft due to the disproportionate width of the fuselage required to accommodate the large propeller diameter. Such a wide bodied fuselage would create a significant drag problem as to be efficiently applied to a fixed wing aircraft application. In a true ducted fan application however, duct depth and diameter as a function of its' blade chord, diameter, and number of blades employed, combine with higher rotational speeds to allow greater thrust in a smaller area over that of a shrouded propeller; this allows for a narrower more aerodynamic fuselage. An additional disadvantage of this prior art craft is the drive means, being hydrostatic, is complex and heavier than a direct drive design. This example of prior art drive train means did not lend itself to adding a horizontal thrusting means.
The Air jeep employed twin engines for a one engine out safety feature at low altitudes. A single engine failure at a moderate altitude however, was sufficient to terminate its' flight even with the remaining engine functioning. The craft can not auto rotate like a helicopter for a safe landing. Lacking wings, and horizontal thrusting means, it could not land horizontally like a twin engine fixed wing aircraft with a remaining engine functioning.
In regard to the prior art apparatuses respecting the Semiautonomous Flight Director device (SFD) invention disclosed herein; all require a skilled pilot. To one degree or another each prior art apparatus either augments skilled pilot operation directly, or affords a skilled pilot a means to better utilize a autopilot.
Flight control and situational awareness and the lack thereof for UAV pilots is of particular concern to UAV manufacturers and users alike, most specifically military and non-military government users. As of the date of this application over eighty five percent of all UAVs currently being flown in the world today will crash as a result of a UAV pilots' lack of situational awareness and the resulting loss of flight control over the UAV flown regardless of any given UAV pilots' skill and/or experience level. These two factors alone, according to current UAV mishap statistics, are of paramount importance to the Federal Aviation Agency (FAA) and the National Transportation -and Safety Board with respect to their authorization for use and implementation of UAV technology in the civilian and commercial aviation sectors.
Disclosed in U.S. Pat. No. 5,255,880 issued Oct. 26, 1993 to Woon Lyloc and David C. Pattison is a manual override apparatus which allows a skilled pilot to override autopilot operation in aircraft that have fly by wire or fly by light flight control systems as opposed to mechanical flight control systems having an autopilot system.
In this prior art device the pilot does not have to disengage the autopilot in order for a skilled pilot to make direct changes to the controls that are under direct autopilot command. The degree of change made by the action of a pilot displacing a given aircraft's manual control stick or yoke is sensed by a circuit when the pilot places a specific amount of force on the control stick or yoke. Once the amount of force level reaches a certain threshold, the amount and degree of deviation, in linear terms, of the pilots' control stick or yoke is subsequently sensed to allow a pilot to make flight control changes under autopilot command but only to the exact degree of deviation made in the pilots' control stick or yoke.
It is important lo note here, that in the application of this prior art device; only a skilled pilot having knowledge and sufficient skill in flying a particular aircraft under non-autopilot operation should make such deviations in the control stick or yoke of such an aircraft having the device and autopilot. The reason for this is that the amount of deviation made in the pilots' control stick is directly related and linearly proportionate to the amount and degree of linear and proportional change effected in the flight controls of the particular aircraft flown by the pilot.
This is to say that a pilot could place the control stick into a position and to such a degree that would cause the flight controls of the aircraft flown under autopilot command to likewise place said aircraft in a negative flight regime. This could result in the loss of aerodynamic control of the aircraft if it were not for the pilots' skill precluding the placing of the control stick in such a position as to cause a negative flight regime.
The advantage of the prior art device is it allows override control of the autopilots' flight controls of a aircraft having a fly by wire or fly by light flight control system whereby a skilled pilot may make changes directly to the flight controls coincident to direct command of an active autopilot governing said aircraft flight controls.
A disadvantage of this prior art device is that it is not applicable to aircraft having flight control systems other than fly by light or fly by wire flight control systems and the system requires operation by a skilled pilot.
U.S. Pat. No. 5,067,674 issued Nov. 26, 1991 to Albert Heyche, Alain Latteur, and Philippe Dekoninck, all of Brussels Belgium, discloses a control system for remote controlled aircraft, which is, in effect, a compensator for variations of time lags associated with the difference in time from the moment a pilot initiates an action by remote control until the aircraft in flight begins to act on the change with respect to the aircraft's resultant attitude change that follows the execution of the various interactions of the aircraft's flight control surfaces.
It is further disclosed in U.S. Pat. No. 5,067,674 that the device automatically compensates for variations in normal operation of a flight control system of a remotely controlled helicopter to prevent negative flight regimes. The prior art device aids, in an automatic manner, a skilled pilot in piloting a remotely controlled helicopter. The system does not however, supplant the skill normally required to pilot a remotely controlled aircraft or helicopter.
U.S. Pat. 4,964,598 issued Oct. 23, 1990 to Zacharaia Berejik, Ramot Tzahala; Allon Wallach, Moshav Talmei Elazar, of Israel discloses an apparatus to automatically stabilize, to a certain degree, a remotely control aircraft in yaw and roll for aircraft turns initiated by a pilot whereby the aircraft is required to bank in order to accomplish the turn.
The apparatus, also in like manner, provides automatic stabilization, to a certain degree, of the pitch of a remotely controlled aircraft for aircraft ascensions and descentions initiated by the pilot.
The apparatus however, does not supplant pilot skill, but rather is an aid to a skilled pilot that automatically compensates to a certain degree for the pilots' lack of situational awareness of the difference between what a pilot perceives to be the actual attitude of a remotely controlled aircraft versus the actual physical attitude of the remotely controlled aircraft when performing certain flight maneuvers. The apparatus does not preclude the pilots' placing the aircraft in a negative flight regime however.
The apparatus allows a skilled pilot to perform flight maneuvers that include negative flight regimes in order to allow a skilled pilot to accomplishacrobatic like flight maneuvers in such a way as to compensate to a limited degree for the lack of the pilots' situational awareness of the actual physical attitude of the remotely controlled aircraft with respect to the pilots' perception of the aircraft's attitude.
U.S. Pat. 4,642,774 issued Feb. 10, 1987 to John P. Ceyntala and Kenneth W. McElreath of Iowa is similar in function to the apparatus earlier mentioned herein and disclosed in U.S. Pat. No. 5,255,880.
The apparatus allows a pilot to make manual flight control deviations under autopilot control and then subsequently return to autopilot control of the aircraft to allow the autopilot to smoothly return to the autopilots' preprogrammed flight regime, or optionally, to a new program set determined by the manual flight control deviations initiated by the pilot.
The primary effect of this prior art device is in allow for over ride changes in an autopilots' control of an aircraft by a pilots' degree of linear displacement of the pilots' control stick either allowing the autopilot to return to its' preprogrammed flight path or alter the preprogrammed flight path in accordance with the degree of linear displacement of the pilot's control stick.
All actions therefore, being accomplished in such a way as to make flight control changes without abrupt flight dynamics resulting from the change initiated by the pilot. Both of the aforementioned prior art devices and the aforesaid prior art device disclosed in U.S. Pat. No. 5,255,880 require a skilled pilot versed in the manual flight operations of the particular aircraft flown and so equipped with said devices so as to preclude the manual placement of the pilots' control stick in such a positions as to cause a negative flight maneuver being initiated by the autopilot.